The term "physiognomy" refers to features of the face, especially so skull - basis of physiognomy when, in the narrow sense, these features are used to infer the relatively enduring character or temperament of an individual. On this site, physiognomy connotes a broader meaning, i.e., it refers to relatively unchanging facial features that might convey messages about any inner or hidden aspect of the person. Most of these facial features have as their basis the bony structure of the skull, on which the soft tissues lie. These features include the shapes and positions of major areas and landmarks of the face, such as the forehead, eyebrows, nose, cheeks, and mouth.

Physiognomy (Gk. physis, nature and gnosis, knowledge) is traditionally a folk science, based upon the idea that the study and judgement of a person's outer appearance, primarily the face, reflects their character or personality. The shortened form "physog" is also a slang word for "face". The term physiognomy is also used to refer to the general appearance of a person, object, or terrain, without reference to its underlying or scientific characteristics. This article will deal with the folk science.

Absolute predictive physiognomy, in which there are believed to be invariable 100% correlations between physical features (especially facial features) and character traits; this has been disproven # scientific correlation physiognomy, in which there are believed to be rough statistical correlations between physical features (especially facial features) and character traits due to a person's physical preferences that are caused by corresponding character traits, such that gene mixing causes the correlations; this type of physiognomy is therefore allegedly based on genetic determinism of character. Although this type of physiognomy has generally been disproven as well, the idea has been revived as personology.